This disclosure relates to a dynamoelectric machine, and more particularly to a rotor angular position and start-up system for a dynamoelectric machine.
In aeronautical applications, it is desirable to use a single machine as both a starter (to start an engine) and a generator (to supply electricity). For example, an aircraft may utilize a single motor to both start an engine and to generate electricity. In another example, an integrated electrical motor may be utilized for starting and driving a fan, compressor, pump, etc., of an aircraft. The motor is sometimes called a dynamoelectric machine because of its dual functionality as a starter and generator. A typical dynamoelectric machine includes a stationary stator and a rotating rotor. The dynamoelectric machine may also include a permanent magnet. Dynamoelectric machines having a permanent magnet are classified into two types: interior buried permanent magnetic motors and surface mounted permanent magnetic motors. In an interior buried permanent magnetic motor, the magnet is buried within the interior of the rotor. Surface mounted permanent magnetic motors are also known that include a magnet that is mounted radially outward from the exterior surface of the rotor.
In some motors, it is necessary to detect a position of the rotor in order to sustain operation of the motor during start-up. The initial rotor angular position is necessary to ensure that the rotor spins in the correct direction to avoid damaging the bearings of the parts being driven by the dynamoelectric machine. Determining an initial rotor angular position typically requires a shaft mechanical sensor that is coupled to a rotor shaft of the rotor. However, in some applications it is not feasible to install a shaft mechanical sensor onto the rotor. Additional benefits of a sensorless control of a dynamoelectric machine include reduced weight, reduced cost and overall reliability improvement of the dynamoelectric machine.
Methods for the sensorless detection of rotor angular position are known. For example, a back EMF method and a carrier injection approach are used to determine an initial rotor angular position prior to start-up. The back EMF method determines the rotor position based on voltage and works well at a high angular rotor velocity. The carrier injection approach explores the spatial saliency of the rotor to determine an initial rotor position. An alternating voltage or current is communicated to the dynamoelectric machine and the resulting current or voltage is measured and analyzed to decode the rotor position information in the carrier injection approach. Both the EMF method and the carrier injection method are effective for interior buried permanent magnetic motors. Disadvantageously, however, neither of these methods has proven effective for a surface mounted permanent magnetic motor. Surface mounted permanent magnetic motors are generally preferred over interior buried permanent magnetic motors because of their ease of manufacturability.
Accordingly, it is desirable to provide an improved rotor angular position and start-up system for sensorless control of a dynamoelectric machine.